A database may implement serializable isolation to avoid or eliminate update conflicts during transactions. When a database implements serializable isolation, the database provides an illusion to a transaction that makes it appear to the transaction that the transaction is the only transaction currently involved with the database. In serializable isolation, the transaction does not have to worry about other transactions concurrently changing data values. To provide a serializable isolation, the database may delay transactions while a particular transaction is allowed to proceed. This may lead to unacceptable performance or concurrency issues.